In chain transmissions, it is common to use a roller chain, a rollerless bushing chain, or a silent chain. Furthermore, hybrid chains in which the features of a silent chain and the features of a roller chain or bushing chain are combined have been used in chain transmissions in which the sprockets are provided with a set of teeth for meshing with rollers or bushings of the chain, and one or more sets of teeth for meshing with toothed link plates in the chain.
A typical chain transmission incorporating such a hybrid chain is shown in FIGS. 15 and 16. In FIG. 15, a chain 510 comprises link plates 511, which function as a silent chain. Link plates 511, each of which has a pair of teeth, are disposed along both sides of the chain in alternating, overlapping, relationship. Link plates 512, which do not have teeth, are disposed in alternating, overlapping, relationship along the inside of the chain, and cooperate with rollers 520 in such a way as to function as a roller chain. The link plates 511 and 512 are connected by connecting pins 530. A sprocket 550, shown in FIG. 16, has teeth 552, which cooperate with the teeth of plates 511, and teeth 551, which cooperate with the rollers 520.
In the operation of the chain transmission, teeth of the link plates 511, which function as a silent chain, engage sprocket teeth 552. When a tooth of a link plate 511 is seated on a sprocket tooth 552, a roller 520 engages a sprocket tooth 551. Further details of the chain transmission just described can be found in Japanese Examined Patent Publication No. Sho. 59-30936.
A chain transmission using a convention silent chain exhibits significant elongation due to wear of its connecting pins, and the elongation of the chain is accompanied by a reduction in its strength. In a chain transmission using a conventional roller chain, obtaining high strength is difficult, especially because of difficulties in strengthening the rollers. Furthermore, conventional roller chains produce a large amount of noise as they come into engagement with a sprocket.
In the hybrid chain describe above, in which the outer link plates function as a silent chain and transmit power, the problem of elongation due to wear of the connecting pins has not been overcome. Thus, as in the case of a conventional silent chain, elongation of the chain occurs, and is accompanied by a decrease in strength. Another problem with a transmission incorporating the conventional hybrid chain is that it generates noise due to vibration at a frequency corresponding to the number of sprocket teeth.
This invention addresses the above-described problems by providing a chain transmission in which engagement noise is reduced, and which avoids a decrease in chain strength due to elongation resulting from excessive wear of the connecting pins.